Re: [PATCH net-next 0/2] Add support for PHY packet generators

From: Andrew Lunn <andrew@lunn.ch>
Date: Wed, 17 Feb 2016 21:32:05 +0100

Some Ethernet PHYs contain a simple packet generator. This can be
useful for bringing up new devices, trying to determine if a problem
lies in the MAC-PHY connection or PHY-Socket. Also, the PHY generators
can generate invalid packets, which is hard to do in software.

Add support ethtool(1) and wire up the Marvell PHY packet generator.

You really cannot make this blocking, every time we've added a blocking
ethtool op that could take a non-trivial amount of time we've been
burnt.

So as Ben mentioned blocking for 0.3 seconds or whatever is a non-starter.